COLUMBUS, Ohio--If you haven't thought much about Ohio's congressional races this election season, don't worry: there hasn't been much reason to.

Every member of Ohio's current congressional delegation - 12 Republicans and four Democrats - appears to be safely assured of re-election in November, with most facing only token opposition from inexperienced, poorly funded political amateurs.

Ohio's still a battleground state this year: Hillary Clinton and Donald Trump are running neck-and-neck in Ohio's presidential race, and the U.S. Senate race (until recently, at least) has stayed close. Why, then, aren't there any competitive races in the Buckeye State for Congress?

Here are four reasons:

Gerrymandering

Thanks to the way GOP lawmakers drew Ohio's congressional districts, almost all of this year's races were over before they started.

When Republicans redrew the state's congressional maps in 2011 (just the second time in at least 60 years that one party controlled the entire process), they predicted that Republicans would win 12 districts and the Democrats four - exactly how the results have turned out.

Republican voters, meanwhile, were spread among the other 12 districts, with the result that the GOP has a reasonably solid advantage in those districts.

Here's how Ohio's 16 congressional districts stand politically, using the Cook Political Report's partisan voting index (which shows, on average, how many percentage points the district deviated Democrat or Republican in the last two presidential elections compared to the national average), and the Ohio Manufacturing Association's political Republican index (which is calculated based on how much support several recent major GOP candidates got in each district). Also included: the vote percentages by district for Democrat Barack Obama and Republican Mitt Romney in the 2012 presidential election.

No open seats

Every current member of Congress from Ohio is running for re-election this year. In fact, every congressional incumbent in Ohio this year, except one, won their past two House races as well (the lone exception is Republican Warren Davidson, who took over ex-House Speaker John Boehner's southwest Ohio district in June).

Incumbents have an advantage in many ways, including name recognition, campaign experience, and (perhaps most importantly) an easier time raising vast amounts of money.

In addition, none of the incumbent candidates, except perhaps Republican U.S. Rep. Dave Joyce, faced significant opposition in the March primary election, meaning they avoided having to spend money or withstand political attacks.

Lack of viable opponents

Those who are running against incumbents are not political A-listers. Of the 16 major-party nominees seeking to unseat the current officeholders, only one has ever held elected office in Ohio: Michael Lorentz, the Democratic mayor of Belpre challenging U.S. Rep. Bill Johnson in southeast Ohio.

U.S. Rep. Brad Wenstrup's Democratic opponent, William Smith, is a truck driver. Richard Morckel, the Republican running against U.S. Rep. Tim Ryan, is an imaging technician. Democrat Robert Klepinger, U.S. Rep. Michael Turner's opponent, is a high school teacher who says he's running to do his civic duty - he has no campaign manager, and his campaign treasurer is his friend's son.

Several of the races are rehashes of the last election: five of Ohio's 16 incumbents are facing the same person they defeated in 2014. (A sixth nominee, William Smith in District 2, was defeated in the 2014 Democratic primary).

Two of those return candidates, both Democrats, are running in Ohio's most competitive districts (relatively speaking): Klepinger in District 10 and Michael Wager in District 14.

Ohio Secretary of State Jon Husted called the election "a waste of time and tax dollars," and a state lawmaker drafted a bill to eliminate primaries when there's only one candidate.

Lack of support

Despite the lack of competition, all of Ohio's congressional incumbents have raised several times as much money than their opponents. Part of that is because it's far easier for sitting members of Congress to take in campaign donations. Opponents, meanwhile, find it difficult to attract money in a race that's not seen as competitive.

Incumbents don't even have to spend their money to benefit from it: having a large war chest scares away potential rivals from entering the race, and they can use the cash to help other candidates or prepare a future run for higher office.